if you are the open friendly guy willing to step-up to the customer and try an sell them something they need. I would go with Instant Honesty and A314. Trust, Respect and Honesty just the vibes you need from a salesperson. Working in a position where I have to sell my ideas, this combination works well. I find people question your recommendations less, possibly because they know your answer is correct.
If you are a little shy, want to come off as a buddy or someone who knows, I would add Instant Openness and some Instant Shine with the above.
If you are trying to sell to women, A314 and some Instant Female Magic and give that relax and trust me vibe.
maybe some Ammo for a spicy sexy vibe.
** Edit-
Also see this thread-